For capturing topographies, e.g. for the purpose of surveying, checking or documentation, optical devices are commonly used which work with optical measuring beams for scanning a surface and capturing of the topography by the distance measurement to points on the sensed surface. A suitable scanning device may be a scanner system, in particular a profiler, which allows for capturing a surface structure by guiding a measuring beam in a scanning manner over the surface and by capturing the spatial position of surface points in the scanning area with a distance measurement relating to the points and linking the measurement with angle information gathered at the time of the measuring beam emission. From the angle and distance information, so called range images of the scanned surfaces may be reconstructed.
A profiler for capturing topographies may also be realised by an electro-optical distance meter, which is guided over a surface area in a scanning manner and which may use laser light.
The correlation of the measurement points of the distance meter on the one hand, to the surface to be captured on the other hand, may e.g. take place by overlaying the scanned area with a reference model of the surface.
A laser distance meter as a surface profiler is for example utilised in the “LEICA Pegasus: Two” system of Leica Geosystems AG.
Fields of application of such surface profilers or systems are e.g. the documentation of structures or the surveying of mines and tunnels. In the latter application, gathering a profile of the hollow space, detecting and measuring of surface variations—like cracks, cavities, gravel nests, detachments or water damages, as well as detecting and measuring of infrastructure—like contact wires, poles and traffic lights—are of particular interest.
In linearly passable hollow spaces, such as rooms, corridors, mines, tunnels, canyons or alleys, the profiler is usually mounted to a vehicle in such a way that the scanning movement of the measuring beam—in a first scanning direction—takes place about an axis which is essentially parallel to the direction of movement of the vehicle, wherein the direction of movement of the vehicle is a second scanning direction.
However, in case the ground of said topography is not equipped with an adequate travel way, such as a sealed street or railway tracks, profilers known from prior art are not practicable, or so only under some losses. A similar problem is represented by surveying tasks in canyons, for a vertical surface of a building, or for a wall of rock, wherein a “ground” for linearly guiding the profiler by a vehicle is not available.